The Hedgehog signaling pathway has recently been implicated in the formation of multiple tumor types in humans and vertebrate animals. One of these tumor types is rhabdomyosarcoma, an aggressive soft-tissue sarcoma histologically related to skeletal muscle. In this proposal we will investigate the mechanisms through which Hedgehog pathway activation causes growth of rhabdomyosarcomas and other myogenic sarcomas. Our initial aim will be to phenotypically identify and isolate tumor stem cells from primary rhabdomyosarcoma cell lines which require Hedgehog pathway activity for growth. We will also survey a variety of primary human and mouse myogenic sarcoma cell lines to determine if the Hedgehog pathway is universally necessary for driving tumor growth. In this survey we will simultaneously determine if other well known tumor-growth driving signaling pathways, specifically Wnt and Notch, have a role in the proliferation of myogenic sarcoma cells. Finally, we will see if the growth driving signaling pathways identified for myogenic sarcomas contribute to the maintenance and/or proliferation of a tumor specific stem-cell population.